How Species Manage to Thrive in Polluted Ecosystems | Environment | All topics from climate change to conservation | DW


In a world where human-made pollution in the form of smog, industrial sewage, fertilizer runoff, dense blankets of ocean plastic and much more invades the planet, many animal and plant species face it. .

But some species have found ways to live and adapt to the pollution that now characterizes their once clean environment.

Plastic-eating microbes adapt to pollution

A team of researchers from Chalmers University of Technology in Gothenburg, Sweden, made a startling discovery last year, when they discovered that microbes living in oceans and soils around the world can evolve to eat plastic, especially if they live in plastic-rich ecosystems. Pollution.

By analyzing microbial DNA samples collected from hundreds of locations around the world, researchers discovered more than 30,000 different enzymes that could degrade 10 types of plastic.

Much of our plastic ends up in the oceans and washed up on beaches

While some of these enzymes had previously been identified in bacteria living in landfills, the vast majority were unknown. Even more impressive was the finding that the amount and type of enzymes found in the samples matched the volume and type of plastic pollution in the places they were taken from.

Microbial DNA collected from the oceans, for example, showed more plastic-degrading enzymes at deeper sea levels where the degree of plastic pollution is generally higher. According to the study, this suggests “that the Earth’s microbiome may already be adapting to current trends in global plastic pollution.” With millions of tons of material dumped into the environment every year, microorganisms apparently face “sufficiently strong selective pressures” to develop these plastic-digesting enzymes.

Adapting to Early Industrial Pollution: A Moth Turns Black

Last year’s findings are not the first to show that species are adapting to environmental pollution.

In the mid-1800s, a decade before Darwin’s theory of evolution was published, residents of increasingly industrial English cities like London and Manchester observed an unexpected color change in the peppered butterfly.

The insect had been characterized by its mottled white body and wings – a pattern used to camouflage the nocturnal animal during the day when it rested on tree trunks and walls. But as industrialization and the resulting air pollution intensified, a genetic mutation that produced an all-black version of the peppered butterfly began to spread within the species.

A pepper butterfly

The distinctive pattern of a pepper butterfly – a butterfly that has not evolved to become black

Known as “carbonaria”, these moths could more easily hide from hungry birds in blackened industrial landscapes.

While white pepper moth remained the common form in the countryside, carbonaria moth had become the dominant variant in the Manchester area by 1900.

Fish in toxic waters

Adapting genetically to heavily polluted habitats can clearly be an evolutionary advantage. But evolving the ability to exist in a polluted environment often comes at a cost. While certain changes in the genome can help a species resist a specific pollutant, they can make the species more vulnerable to other environmental stressors.

This is the case with the killifish, a small silvery fish that thrives in the toxic waters of the northern Gulf of Mexico and the Atlantic coast of North America.

High concentrations of heavy metals, dangerous chemicals discharged from industrial waste and residues from the production of herbicides like the infamous Agent Orange have made these waters deadly to vertebrates. Polluting substances can disrupt the development of embryos, cause deformities and heart defects or prevent their hatching.

Although killifish are generally sensitive to brackish water, a study of Atlantic killifish by Andrew Whitehead of the University of California, Davis suggests that “even at the most contaminated sites, where killifish should not not persist, they seem to thrive. “

A fondue

Some species of killifish have become accustomed to living in highly polluted waters

Populations living in contaminated areas along the Atlantic and Gulf coasts carry a genetic variation that makes them resistant to the disastrous effects of toxic chemicals. Thanks to their genome, fish can withstand a concentration of chemical pollutants thousands of times higher than the normally lethal dose.

Although this genetic change made the Killifish more resistant to toxins, it also reduced the species’ tolerance to low oxygen levels. This is a problem because oxygen levels in the sea vary, and as global temperatures rise, the oxygen in the oceans is expected to drop significantly. Once the water has been cleaned of pollutants, adapted fish may have a harder time surviving than those without the variation.

Few species able to adapt

Most animal and plant populations will not be able to genetically adapt at all to their polluted environment. It only worked for a few of the millions of species.

What has allowed microbes, moths and the killifish to adapt to high pollution levels is a rapid rate of reproduction as well as incredibly large population sizes – the killifish, for example, is l most populous animal species with a backbone in many urban estuaries.

A species with a large population is much more likely to develop genetic mutations that increase resistance to environmental stressors. But most species threatened by toxins lack the population size needed to develop adequate mutations. Cleaning up polluted sites and avoiding pollution in the first place is the only way to save them.


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